Jeremy Beck's picture

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  by  Jeremy Beck

“The best hosts for many diseases are often the very species that thrive when humans disturb habitats and diversity declines” - ecologist Felicia Keesing

Immigration-driven population growth is devouring natural habitat in the United States, threatening wildlife and biodiversity. This raises ethical questions about our responsibility towards our non-human neighbors and surroundings, but we also have a naked self-interest in arresting immigration-driven population growth in order for wildlife and biodiversity to thrive. Writing in The New York Times Magazine Ferris Jabr says we have altered the natural world to a point where zoonotic diseases can spread to humans more efficiently than ever. Money quote:

In 1700, true wilderness still covered nearly half the continents. We have now directly modified more than 70 percent of Earth’s ice-free land. More than a third of the forest that existed before the dawn of agriculture is gone. A few select species have proliferated in the new anthropocentric world, primarily to serve our needs: wheat, corn, chickens, cattle. Certain dogged and weedy creatures thrive in and around our homes. In general, however, the meteoric rise of humans has brought the cataclysmic decline of wildlife. The planet is currently losing its biodiversity at 100 to 1,000 times the prehuman extinction rate. We have reduced the total mass of wild mammals by 82.5 percent, fish by 83.75 percent and plants by half.

At the same time that we devastate wildlife and eliminate entire species, we squeeze the creatures that remain into perverse and dangerous configurations, ultimately jeopardizing our own health. Zoonoses reveal that environmental stewardship is not simply related to public health; in many cases, they are the same.

In the United States, the destruction of ecosystems and habitat is primarily the result of population growth. And the United States government has set immigration levels so high that we are projected to grow by more than 100 million people over the next four and a half decades. Jabr's example of the Hudson Valley in the Northeast United States gives us an idea of what that could mean for our resilience (emphasis, mine)

Expanding human populations are fracturing forest into increasingly tiny islands of green throughout the Northeast. The average patch of contiguous forest throughout much of the Hudson Valley is now a mere 182 acres, just over 20 percent the size of Central Park. Slivers of forest lack the space and diversity of resources required by many large mammals, such as wolves and lynxes, and by highly specialized creatures, such as some woodpeckers and pollinators that feed exclusively on a few plant species.

In fragmented wilderness, where many creatures cannot survive and species diversity is low, white-footed mice populations boom and infect huge numbers of ticks with the bacteria that cause Lyme, escalating the risk to humans.

Conversely, in high-diversity areas, populations of white-footed mice are constrained by numerous competitors and predators, most of which are far less likely to infect ticks with Borrelia, mitigating the risk of spillover, a phenomenon known as the dilution effect.

Since the 1990s, when [ecologists Felicia Keesing and Richard Ostfeld] began their studies, researchers working in many different ecosystems have discovered that high biodiversity often dampens the risk of infectious disease. “The best hosts for many diseases are often the very species that thrive when humans disturb habitats and diversity declines,” Keesing told me. “Eventually we realized that what we thought was a peculiarity of the Lyme disease system was happening all over the planet."

"We are used to thinking of ourselves as the protagonists of every landscape," Jabr concludes, "but from the perspective of infectious microbes, we and other large creatures are the landscape."

Read more at The New York Times (subscription required).

Updated: Fri, Jul 10th 2020 @ 10:40am EDT

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